1. Technical Field
The present invention relates to an oscillation circuit, an oscillator, an electronic device, a moving object, and a manufacturing method of the oscillator. For example, the invention relates to an oscillation circuit provided with a temperature compensated circuit which compensates for frequency fluctuation according to a change in an ambient temperature.
2. Related Art
An AT cut quartz crystal resonator which constitutes a temperature compensated quartz crystal oscillator (TCXO) draws a curve which is approximated with a three-dimensional curved line having a point around 25° C. as an inflection point according to a change in an ambient temperature, and thus a frequency fluctuates. In the TCXO, a voltage signal which compensates frequency fluctuation is generated by a temperature compensated circuit, and is applied to a varicap diode provided in an oscillation circuit. According to this, the frequency fluctuation due to a change in an ambient temperature is suppressed, for example, high frequency accuracy which is ±0.5 ppm in a temperature range of −40° C. to 85° C., is realized. Since three-dimensional temperature characteristics change by variations between each solid of quartz crystal resonator, a voltage output by the temperature compensated circuit is delivered after being adjusted so that the most appropriate temperature compensated voltage is individually obtained in the TCXO. In recent years, a size of the TCXO has been reduced, and there is a case where a test terminal which monitors and inspects the voltage from the temperature compensated circuit and a functional terminal (for example, an output terminal) of an oscillator are used together. For example, when testing the temperature compensated circuit in a case where the test terminal and the functional terminal are used together, an output circuit is in an OFF state and the temperature compensated voltage is monitored by the output terminal. The output circuit is in an OFF state when monitoring the voltage, and the output circuit is in an ON state when normally operating and an oscillation signal is output to the output terminal. For this reason, since the operation of the output terminal when testing the temperature compensated circuit and the operation of the output terminal when normally operating are different from each other, a self heat generation amount of the oscillator itself changes and a temperature in the oscillator changes. As a result, in a case where a circuit, such as the oscillation circuit, in the oscillator shows a change in characteristics due to a temperature change, even when the temperature compensated circuit is tested and the frequency of the oscillation signal is adjusted, there is a problem in that the oscillation signal when normally operating is deviated due to the temperature change in the oscillator, and the frequency cannot be temperature-compensated with high accuracy.
In order to solve the problem, in JP-A-2013-162358, an oscillator provided with a heat generation circuit in which a signal is input from the oscillation circuit when the output circuit is in an OFF state and heat is generated, and which stops the operation thereof when the output circuit is in an ON state, is suggested.
According to the oscillator described in JP-A-2013-162358, since the heat generation circuit which generates the heat when the output circuit is in an OFF state is provided, for example, it is possible to match the heat generation amount when adjusting the temperature compensated circuit and the heat generation amount when the oscillation circuit operates, and to perform an adjustment of the temperature compensated circuit in a similar state to a state of an actual operation. However, a dedicated circuit for generating the heat, for example, a circuit which is equivalent to the output circuit (buffer circuit or the like) is required, and the heat generation circuit generates the heat using the signal of the oscillation circuit as an energy source. For this reason, there is a possibility that an AC signal which is generated from the heat generation circuit when adjusting the temperature compensated circuit has an effect such as noise.